Abiotic degradation of field wheat straw as a notable source of atmospheric carbonyls in the North China Plain.

Abstract Carbonyl compounds (carbonyls) play a crucial role in atmospheric chemistry, but their atmospheric sources are not fully identified. Here we show notable influence of unexpectedly high carbonyl emission from field returning wheat straw on atmospheric oxidants over the North China Plain (NCP). The emission of carbonyls exhibits distinct diurnal variation with the noontime peak value greater than 135 μg∙kg−1 (dry straw weight) ∙h−1, which is mainly attributed to biomass abiotic degradation processes that are affected by air temperature and sunlight intensity. The carbonyl emission can result in the increase of mean daytime O3 concentration over the NCP by 6% through model simulation, which may be one of the important reasons for the occurrence of the most serious O3 pollution in June when winter wheat is concentrated harvested in the region. To mitigate the serious O3 pollution and reduce carbon emission, the crop straw is better used for energy, rather than being returned into field.